Sanding not only feathers out chipped paint but also provides "tooth" for the next coat of paint. For glossy trim, use a sanding sponge rather than sandpaper. Sponges mold to the shape of the trim and last longer than paper. When applying latex over alkyd paint or when he is not sure of the original finish, Brian Doherty, a painter in Richmond, Virginia, follows the hand-sanding with liquid sandpaper to make sure the surface is completely deglossed to prevent incompatibility problems. "I've seen homes where latex was used on oil-painted trim, and the paint started to peel in less than a year," says Doherty.
In Mark Twain's classic "The Adventures of Tom Sawyer," Tom tricks his friends into painting his aunt's fence. You probably won't get that lucky, but there are good reasons many homeowners keep their painting in-house. No building codes apply to interior decoration; if you do something dumb, you don't risk life and property as you would if you were, say, tackling a rewiring job; and because labor typically accounts for 80 to 85 percent of the price of a paint job, you'll save a ton by doing the work yourself.
The last big decision is how to apply the paint. Most pros use paint sprayers because they're fast, but in inexperienced hands a high-powered sprayer can leave drips, thin coats, and a mist that may land on many things other than your siding. If you do hire a painter who uses a sprayer, make sure he is meticulous about removing, covering, or masking off everything in the area that might get hit with overspray: gutters, roofs, windows, shrubbery, walkways, cars—you name it.
The right paint stroke to use in interior painting is highly debatable. It's not a talent as much as a skill that is learned through practice. Many experts paint in a “W” pattern when using foam rollers, but others simply roll up and down then sideways with either brushes or rollers. The motion isn’t as important as making sure that the application is even and drip-free across the entire area. However, technique is important when you're covering over wall repairs.